Surge arrester with a mtal oxide resistor

ABSTRACT

In a surge arrester with a multi-column arrangement of the metal oxide resistors within an insulating housing, each column is to be made of resistance elements in a mechanically self-supporting structure. To this end, the resistance elements of each column are arranged between two holding plates intercon-nected by holding rods. The individual columns, called &#34;modules&#34;, are arranged to be individually centered on a plate fitted at the lower end of the insulating housing.

BACKGROUND OF THE INVENTION

The invention, which is in the area of protective engineering for energydistribution facilities, is concerned with the structural configurationof a surge arrester, with an insulating housing and with a metal oxideresistance arranged inside the insulating housing, such that the metaloxide resistor consists of two or more columns, connected electricallyin parallel, made up of a larger number of resistance elements, of whicheach column has two separate holding plates between which the resistanceelements of the column are arranged, and which in turn are joined bymeans of insulating holding rods which laterally immobilize theresistance elements.

Surge arresters with a metal oxide resistor as the shunting elementgenerally consist of a plurality of flat cylindrical resistance elementsarranged in columnar fashion one above the other, the column formed bythese resistance elements being arranged inside a ceramic or plasticinsulator tightly sealed at the top and bottom ("IEEE Transactions onPower Delivery," Volume PWRD-1, No. 1, January 1986, pp. 151-156; FIG.6).

To increase the energy handling capacity or to reduce the residualvoltage, it is common in the case of metal oxide shunts to connect aplurality of resistance columns made up of individual resistanceelements in electrically parallel fashion. For this purpose, two to fourcolumns are arranged next to one another, inside a common insulatinghousing, on a support plate by means of which they are inserted into thecommon housing. This is known, for example, from U.S. Pat. No.4,326,232.

SUMMARY OF THE INVENTION

The invention creates a surge arrester structure which improves theindividual columns in terms of handling and accessibility formeasurement purposes. Proceeding from a surge arrester with the featuresof the preamble of claim 1, the columns are arranged at the lower end ofthe insulating housing on a plate, centered with respect to the axis ofthe insulating housing, and a separate compression spring is associatedwith each of the columns for contact purposes.

A configuration of this kind thus provides for each individual column,made up of resistance elements, to constitute an independent modulewhich represents a mechanically self-supporting structure. Theparticular required number of these modules is placed next to oneanother in the insulating housing, and mechanically and electricallyjoined together and immobilized at both ends by suitable structuralmeans. The assembly of multiple modules, standardized in this fashionand completely identical to one another, yields a substantialsimplification in production. In particular, the individual modules areeasy to handle during assembly of the surge arrester. Furthermore, it ispossible to evaluate the individual modules before complete assembly ofthe surge arrester, and thus determine current distribution. Withreference to the operation of this kind of surge arrester, separateconstruction of the individual resistance columns allows displacement ofthe modules with respect to one another when the suppressor isoverloaded, thus opening up a pressure relief channel of the greatestpossible cross section in the region of the active arc. Thisdisplaceability can be ensured by suitable structural measures at thetop end--and, if necessary, also at the bottom end--of the individualcolumns.

Because contact with each individual resistance column is made by aseparate compression spring, a contact pressure of substantially equalmagnitude, and thus a transition resistance of equal magnitude, isachieved for all the modules.

BRIEF DESCRIPTION OF THE DRAWINGS

An exemplary embodiment of the invention is depicted in FIGS. 1 and 2,in which:

FIG. 1 shows a vertical section of the housing with a view of thesuppressor element; and

FIG. 2 shows a cross section through the suppressor in the region of thelower end.

DETAILED DESCRIPTION

FIG. 1 shows an surge arrester whose housing consists, in a knownmanner, of ceramic insulator 1 and a metal foot part 2 and a metal headpart 3. The housing could also be made of a plastic. Arranged at thelower end of ceramic insulator 1 is a plate 4 in the form of a bearingbracket, which is immobilized by means of a mounting ring 41, such thatthis mounting ring also immobilizes a membrane 42 and a sealing ring 43.Also joined to plate 4 is a superposed cruciform web member 44, on whichthe columnar resistance modules 6 are braced. These modules consist of aplurality of resistance elements 64, arranged one on top of another,which are located between the lower holding plate 61 and upper holdingplate 62, the holding plates being joined together by means of threeholding rods 63 arranged with uniform spacing at the circumference.Fastened in each case to the lower holding plate 61 is a block-likespacer 5, by means of which the respective columnar module 6 ispositively centered in the cruciform web member 44.

Also arranged on the upper holding plate 62 is a spacer 7 on which acompression spring 8 rests. Also provided, in shared fashion for allcolumnar modules 6, is a contact plate 9 which is placed under pressure,with the interposition of pressure pieces 10, by pressure ring 11 joinedto head part 3, and by pressure plate 13. Pressure plate 13 furtherserves to immobilize the upper membrane 12 and associated sealing ring.

According to FIG. 2, four columnar modules 6 are arranged inside ceramicinsulator 1. Holding plates 61 and 62 of the modules are triangular inshape, in order to ensure the least possible radial expansion of thesurge arrester as a whole.

We claim:
 1. A surge arrester with an insulating housing having a metaloxide resistor arranged inside the insulating housing, such that themetal oxide resistor consists of two or more electrically parallelconnected columns, which are made up of a larger number of resistanceelements, of which each column has two separate holding plates betweenwhich the resistance elements of the column are arranged, and which inturn are joined by means of insulating holding rods which laterallyimmobilize the resistance elements,wherein the columns are arranged on aplate at the lower end of the insulating housing, and centered withrespect to the axis of the insulating housing, wherein a separatecompression spring is associated with each of the columns for contactpurposes.
 2. The surge arrester according to claim 1, wherein theholding plates are triangular in shape.
 3. The surge arrester accordingto claim 1, wherein each column is independently positioned in theinsulating housing.